Recently, hybrid vehicles (HV), plog-in HVs (PHV), and electric vehicles (EV) have become popular. A key device mounted in these eco-friendly cars is a secondary battery. Nickel hydride batteries and lithium-ion batteries are most popular on-vehicle secondary batteries. It is expected that the popularity of lithium-ion batteries will be accelerated in the future because of high energy density and absence of memory effect.
Because on-vehicle secondary batteries can achieve high output and high capacity, a large number of unit cells are connected for use. Normally, on-vehicle secondary batteries are provided as battery packs in which a plurality of battery blocks are connected. A plurality of unit cells are arranged in each battery block. On-vehicle secondary batteries provide high output and clear high safety criteria so that a thermal process carries weight. In principle, secondary batteries in which lithium-ion batteries are used produce larger heat than other batteries.
[patent document 1] JP2007-141511
[patent document 2] JP2011-171175